In a modern semiconductor process fabrication facility (“fab”), work material (e.g., substrates such as silicon wafers) may be stored and transported in protective containers (referred to herein as “substrate carriers”). One example of a substrate carrier is a FOUP (front opening unified pod). A FOUP may carry a number of substrates at once and may include a front door which may be opened to allow access to the substrates. FOUPs may be transported between various components of the fab by automated handling equipment, for example.
When a piece of process equipment (a “tool”) within the fab is finished processing the work material (“processed substrates”), the tool may sit idle while waiting for the automated handling equipment to remove the processed material (e.g., substrates), move away from the tool, and return to the tool with a new batch of substrates to be processed (“unprocessed substrates”). For example, the automated handling equipment may move a FOUP from a load port, move away from the load port, and put the FOUP in local storage; and then return to the load port with a full FOUP of substrates (e.g., silicon wafers) to be processed. The wait time to exchange work material may be significant, such as 5 to 10 minutes or more, depending on the speed of the handling system and the distance between transport locations. When the wait times are multiplied hundreds of times to reflect the number of steps in a semiconductor fabrication process, for example, they may become a significant factor in overall tool productivity in the fab.
Additionally, as process equipment becomes faster, and as the number of pieces of work material in the FOUP decreases, such as in small lot manufacturing scenarios where the FOUP capacity is about 1 to 12 substrates, the exchange-induced idle time may further negatively impact process tool utilization and productivity. This is because the exchange time may become a greater proportion of an overall material throughput time of a given tool. Thus, for small lot manufacturing, for example, exchange time may become a driving factor in tool productivity. Accordingly, faster work material exchange methods, systems and apparatus are desired.